The invention relates to a vaccination gun for medicinal purposes, and particularly to such a gun which is provided with an arrangement to maintain the gas pressure for the drive motor of the vaccine pump substantially constant.
In claim 1 of German Patent Specification 1 922 569 a vaccination gun is described in which the vaccine pump is operated by a motor driven by gas. This gun has the disadvantage that with differing gas pressures, caused, for example, by changing gas pressures in the gas storage container, the motor transfers different forces on the vaccine pump and thus causes, in dependence of the gas pressure, the vaccine to be injected at varying depths into the tissue. For medicinal reasons, however, the injection pressures at the muzzle of the vaccine nozzle should not exceed about 270-300 bar. However, a freshly filled gas bottle produces injection pressures of up to about 750 bar, so that the vaccine is projected far deeper than is safe or desirable into the tissue.